The present invention relates to a noise absorbing apparatus for absorbing noise superposed on a signal transmitted through a cable and, more particularly, to a noise absorbing apparatus in which a closed magnetic circuit is formed to absorb noise with ferrite members so as to enclose a cable, and which can be fixed and supported on an electronic equipment, e.g., a chassis.
In an electronic equipment, e.g., a computer, that processes digital signals, when noise is superposed on a signal transmitted through a cable and enters the equipment, it causes malfunction of the equipment. For this reason, various types of noise absorbing apparatuses have recently been proposed. For example, a pair of ferrite members divided in the radial direction are brought into contact with each other to sandwich a cable between them, and the cable is enclosed with these ferrite members to constitute a closed magnetic circuit. The noise superposed on the cable is absorbed, thereby preventing noise from entering the equipment.
In order to improve the noise absorbing effect of a noise absorbing apparatus of this type, the position of the apparatus in the longitudinal direction of the cable is preferably fixed at a predetermined position. More specifically, when a noise absorbing apparatus of this type is to be put into practical use, the position of the apparatus with respect to the cable where the noise absorbing effect is most conspicuous must be obtained through experiments or the like, and the noise absorbing apparatus must then be fixed at the obtained cable position. For this purpose, conventionally, an arrangement for fixing the noise absorbing apparatus with respect to the cable is provided.
For example, in Japanese Utility Model Laid-Open No. 63-39997, projections are formed on the inner edges of cable insertion openings respectively formed in covers that support a pair of ferrite members. When the covers are closed and the ferrite members are coupled to each other, the projections clamp or bite into the outer coating of the cable to fix it. With this arrangement, however, since the projections are formed fixedly, if the diameter of the cable is small, the projections do not sometimes come into contact with or bite into the outer coating of the cable. If the cable has a large diameter and the outer coating is highly rigid, the covers cannot sometimes be closed.
In order to cope with these problems, regarding a cable arranged to extend along the chassis or panel (to be referred to as chasses hereinafter) of the electronic equipment, the noise absorbing apparatus may be fixed to these chasses, and the cable may be inserted in the noise absorbing apparatus. For this purpose, for example, a cable tie or belt insertion hole may be formed in part of the noise absorbing apparatus, a clamping belt may be inserted through this belt insertion hole, and the noise absorbing apparatus may be fixed by using this belt. Alternatively, the noise absorbing apparatus may be directly fixed to the chasses with screws or the like.
In this case, however, in order to fix the noise absorbing apparatus to the chasses, when the cable is set on the chasses, the noise absorbing apparatus must be simultaneously fixed by clamping the cable tie or belt, leading to a cumbersome fixing operation. In particular, when the noise absorbing apparatus is to be fixed at a narrow place in an electronic equipment, the fixing operation becomes very difficult. In order to simplify the fixing operation, the noise absorbing apparatus may be fixed with a double-coated tape or the like. Then, however, once the noise absorbing apparatus is fixed, it is difficult to remove the cable and the noise absorbing apparatus from the chasses for allowing maintenance of the cable.